(a) Field of the Invention
The present invention relates to a hybrid vehicle. More particularly, the present invention relates to a system for controlling engine starting of a hybrid vehicle and a method thereof which prevents torque impact when controlling the engine starting by using a clutch slip.
(b) Description of the Related Art
Research into eco-friendly vehicles has increased because of the demands for enhancement of fuel efficiency and reinforcement of exhaust gas regulations. A hybrid vehicle is one type of eco-friendly vehicle that has attracted public attention.
Hybrid vehicles use an engine and a motor as power sources. By selectively using the engine and motor as the power sources, hybrid vehicles are capable of enhancing energy efficiency and reducing exhaust gas.
In order to minimize cost and torque loss in hybrid vehicles, a clutch operated by fluid, instead of a torque converter, is mounted between the engine and the motor. In addition, an idle stop and go (ISG) device can be mounted in the hybrid vehicle. The ISG device stops the engine in an idle state and restarts the engine when the engine should be operated according to a driver's will and the vehicle's conditions. Therefore, the ISG device further enhances fuel efficiency and reduces exhaust gas.
In a hybrid vehicle, the engine is started by using the ISG device or by slipping the clutch, which is located between the engine and the motor, when the vehicle speed is faster than a predetermined vehicle speed. If the shift-speed is low in an automatic transmission (for example, the first forward speed or the second forward speed) or the ratio of an output speed to an input speed (i.e., speed ratio) is high (for example, 3:1) in a continuously variable transmission, then when the engine is started by using the clutch slip, frictional resistance of the engine is transmitted to the vehicle body as a large torque and vibration occurs. Therefore, if the engine is started by using the clutch slip, driving performance and ride comfort may be deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.